1. Field of the Invention
This invention relates to a sheet delivery device adapted for use in a paper feeding device of a corrugated cardboard box making machine and the like.
2. Description of the Prior Art
Describing a conventional sheet delivery device used in a paper feeding device of an ordinary corrugated cardboard box making machine with a reference to FIGS. 3, 4 and 5, reference numerals 1a through 1n indicate corrugated cardboard sheets, 2 is a front stopper, 3 is a back stopper, 4 is a gap, 5 is a print cylinder, 6 is a lever, 7 is a link, 8 is a moving suction box, 9 is a suction hole, 10 is a slidable pipe section, 11 is a rotary valve, 12 is a suction tank, 13 is a suction blower, 14 is an upper feed roll, 15 is a lower feed roll, 16 is a crankshaft, 17 and 18 are gears, 19 is a reduction gear and the like, 20 is a motor, 22 is a crank lever, 23 is a grooved lever, 24 is a receiving roll, and 25 is a gear. The corrugated cardboard sheets 1a through 1n supplied from a preceding process are piled in a space surrounded by the front stopper 2, side guides (not shown) and back stopper 3. In order to prevent the whole weight of the piled sheets from being applied to the lowest corrugated cardboard sheet 1a, the sheets are divided into two stacks or layers by the back stopper 3 and one stack is piled on the other. At the lowest corrugated cardboard sheet 1a is delivered through the gap 4 which is formed at the lower end of the front stopper 2 and designed so as to permit passage of that lowest one 1a, the lowest corrugated cardboard sheet out of the upper stack falls on the lower stack. Delivery of the corrugated cardboard sheet 1a is carried out by the moving suction box 8 which performs reciprocation in a sheet delivery direction in response to rotation of the print cylinder 5 via the crank lever 22, grooved lever 23, lever 6 and link 7. Specifically, in response to one revolution of the print cylinder 5 the crank lever 22 rotates one turn and the mechanism composed of the grooved lever 23, lever 6 and link 7 performs one reciprocative swing, this being transmitted to the suction box 8. A portion of the moving suction box 8 which contacts the lowest corrugated cardboard sheet 1a is formed with a number of suction holes 9 (see FIGS. 4 and 5). The interior of the moving suction box 8 is connected to the suction blower 13 through the sealed slidable double pipe mechanism 10, rotary valve 11 and suction tank 12. The rotary valve 11 operates such that it exerts a suction pressure only while the moving suction box 8 is advancing in response to swinging of the lever 6 which is synchronized in timing such that one corrugated cardboard sheet 1a can be delivered in response to one revolution of the print cylinder 5. In response to the above, the moving suction box 8 sucks the corrugated cardboard sheet 1a and moves the same through the gap 4 formed at the lower end of the front stopper 2 thereby to deliver in the direction of the arrow at the same rate as the circumferential speed of the print cylinder 5. The thus delivered corrugated cardboard sheet 1a is pushed to a nip section between the upper feed roll 14 and lower feed roll 15 and then sent to the print cylinder 5 and receiving roll 24 of a succeeding process step. The print cylinder 5, upper and lower feed rolls 14, 15, and crank lever shaft 16 are coupled through the gears 17, 18, 25, reduction gear 19 and the like to the motor (single driving source) 20 and driven thereby.
In operation of the conventional sheet delivery device shown in FIGS. 3, 4 and 5, the corrugated cardboard sheet 1a delivered by the moving suction box 8 shows some variation in delivery timing and an error appears in a following process step (such as a printing process). Specifically, a deviation of timing appears frequently in cases as follows: (1) if the sheet is delivered at high speed (in this case, although the corrugated cardboard sheet 1a follows the movement of the moving suction box 8 after suction is applied, there exists some time lag before the moving suction box 8 exerts its suction effect), (2) if the corrugated cardboard sheet 1a has a warp as shown in FIG. 5 (in this case, due to the presence of the gap 21 such a corrugated cardboard 1a needs additional time after it is sucked before it should be moved; thus, it tends to be fed obliquely), (3) if the corrugated cardboard sheet 1a has a small coefficient of surface friction (such as a coated sheet in this case, slippage tends to occur between the sheet and the moving suction box 8).